define pinking

[james butler]

can anyone tell me exactly what pinkin is and what it sounds like + wot are likely causes.
fanx
james

[Dr. Dub]

Correct me if I'm wrong, but isn't it pre-ignition caused by the timing being too advanced?

[bluestreak56]

Under load a tapping / tappety noise made by the engine usually caused by as dr.dub said either timing too advanced.

Incorrect fuel mixture (try super unleaded)

or the tappets needing lubrication?

Correct me if im wrong also as im still learning myself.. I had this issue switched to tesco 98 ron and retarded the timing. Its still there but should be ok once I sort the fuel mixture and reset the timing again..

[markh]

It can also be caused by heavy carbon deposits around the valves.

[Nate]

It can also be caused by heavy carbon deposits around the valves.

can be helped with a strong dose of redex. run the tank down low then put a full bottle of it in without refuelling. also try pouring it down the spark plug holes (see instructions on the bottle)

[james butler]

yeah that sounds about right. i get the tappety noise under load. i will check my timing and will ave a look at the fuel mixture, as you say it might be a little too lean.

[the edmundator]

It's probably worth pointing out that all sciroccos (at least all 1.8s - carb or injection) were designed to run on at least 98RON petrol.

[SCOTMCDOT]

It is called pinking because when you hear the engine run it does literally make a 'pink, pink, pink' kind of metallic noise as the tappets move.

Try some Redex first and if it continues look at the timing.

[GT Matt]

Correct me if I'm wrong, but isn't it pre-ignition caused by the timing being too advanced?

Ok folks - quick lesson:

Pre-ignition (as it name suggests) is when combustion occurs before the spark (pre). As previously suggested, this can be caused by a carbon build up in the combustion chamber but can also be caused by the cylinders being simply too hot. This could be caused by an engine running too hot (low on coolant/faulty thermostat/corroded or damaged water pump/low on oil/incorrect valve clearences (too small)/head gasket failure etc etc). Strangely, it can also be caused by 'pinking'

Pinking (Detonation) is when the combustion is still ignited by the spark but occurs too early. Excessive pinking will then cause the cylinders to become too hot and potentially lead to pre-ignition. Pinking is usually caused by incorrect (advanced) igniton timing and can usually be cured by adjusting said timing. However, if the pinking has been going on for a while, it can cause faults within the cylinder (like excessive carbon build up from incomplete combustions) that lead to pre-ignition. It could also be caused by a bad batch of fuel. I have seen this quite a few times and is simply cured by filling the tank with new fuel.

Either way, both are bad news and need sorting. The noise you get from both these conditions is the combustion trying to force the piston back down the cylinder in the opposite direction - not nice!!

First I would get, get your ignition timing checked and, as previously suggested, bang some redex in your tank. Check your engine running temp and check you coolant level and for coolant leaks. Check your oil level as oil also acts as a coolant. If this doesn't rectify it, you could try a 'block test' to check the condition of your headgasket. If all these ok, further internal investigation will be needed.

Cheers

Matt

[james butler]

the main reason i ask is 2 weeks ago i drove 150 miles down to isle o wight, the car then started to play up tryin to get started in the mornings. sounded like she was runnin on 3 cylinders untill it got warm and i only had intermitant misfire. this got worse daily to the point i was getting permenant misfire and backfire, i took it to a garage and found that No1 sparkplugs ceramic nose had cracked in two and the nose all crappy(covered all over in light brown coating, 2,3 and 4 had white ceramic nose with few deposits) where it hadnt been firing properly. new set of plugs cured the back fire but found the car now intermitantly misfires only noticable at idle, but thought the car was essentially fixed. drove the car home and have done 300 miles since but the misfire is gettin a bit wose, i took the plugs out today and No 1 is fouling up(light brown coating all over electrodes and ceramic nose, but 2,3 and 4 are still white ceramic with few deposits like new) again, i have checked compression in all 4 cylinders and they all seem ok, arond 14.3bar across all 4. cleaned up the dizzy cap and roter as the contacts were a bit crispy!but this has had no effect. drivin the car, it drives ok just a really annoying misfire that gets worse as that No1 plug fouls up. anyone got any ideas?
it does loose a bit of coolant through the expansion tank cap which ive replaced twice but still leaks. theres no exessive white smoke comin from exhaust. headgasket was my first reaction, hense why i did the compression test. oils not mixing with water with no oil loss and no smoke at exhaust.

[james butler]

have found the problem, my headgaskets goin, waters leakin v slowly into the combustion chamber. this in turn was knackerin up ma sparkplug, have head off now and have given it a gud goin ova n cleanin, u can actualy see where the internals in No1 cylinder have been "steam cleaned".

[GT Matt]

Hi

Glad you got to the bottom of this

If you've still got your cylinder head off, it would be worthwhile having the head both pressure checked (for cracks) and potentially skimmed (as it may no longer be a totally flat surface)

Cheers

[james butler]

yeah cheers, ive had it skimmed n tested and its ok. ive lapped all the valves in and changed all the valve stem oil seals while i was at it. have got the head back togetha and bolted to the block. just waitn 4 a new timing belt kit now to finish it off.